Copybara 26.7.3254

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Copybara for .NET

A tool for transforming and moving code between repositories — a C# / .NET 10 port of Google Copybara.

Copybara transforms and moves source code between repositories. A common use case is keeping an internal (confidential) repository in sync with a public one: you declare a workflow that reads changes from an origin, applies a chain of transformations (move files, replace strings, scrub metadata, …), and writes the result to a destination, recording state in the destination commit message so the process is stateless and reproducible.

Configuration is written in Starlark (the Python-like dialect used by Bazel) in a file conventionally named copy.bara.sky.

core.workflow(
    name = "default",
    origin = git.github_origin(
        url = "https://github.com/google/copybara.git",
        ref = "master",
    ),
    destination = git.destination(
        url = "file:///tmp/foo",
    ),
    # Copy everything but don't remove README_INTERNAL.txt if it exists.
    destination_files = glob(["third_party/copybara/**"], exclude = ["README_INTERNAL.txt"]),
    authoring = authoring.pass_thru("Default email <default@default.com>"),
    transformations = [
        core.replace(
            before = "//third_party/bazel/bashunit",
            after  = "//another/path:bashunit",
        ),
        core.move("foo/bar", "baz/bar"),
    ],
)

About this repository

This repository is a port of Copybara from Java to C# targeting .NET 10, distributed as a .NET global tool named copybara.

• The original Java/Bazel implementation is preserved, unmodified, under java/ and is the reference for behavior. Its original README lives at java/README.md.
• The C# port lives under src/ and tests/.
• CLAUDE.md documents the architecture, porting conventions, and Java→C# mappings. TODO.md is the living work breakdown and status.

Status: the port is a work in progress. See TODO.md for what is implemented and what remains.

Layout

src/
  Copybara.Common/   Guava-like helpers (Preconditions, ImmutableListMultimap)
  Starlark/          Port of the Starlark interpreter (net.starlark.java)
  Copybara.Core/     The engine (origins, destinations, transformations, git, …)
  Copybara.Cli/      The `copybara` .NET tool entry point
tests/
  Copybara.Tests/    xUnit tests
java/                The original Java/Bazel implementation (reference only)

Building

Requires the .NET 10 SDK.

dotnet build Copybara.slnx
dotnet test  Copybara.slnx

Installing

dotnet tool install --global Copybara
copybara migrate copy.bara.sky

Running

# From source:
dotnet run --project src/Copybara.Cli -- migrate copy.bara.sky

# Packaged as a global tool from a local build:
dotnet pack src/Copybara.Cli -c Release
dotnet tool install --global --add-source src/Copybara.Cli/nupkg Copybara
copybara migrate copy.bara.sky

Notable porting decisions

• Git operations use the LibGit2Sharp NuGet package, with a fallback to invoking the git binary for features it does not cover.
• Regular expressions use the native .NET regex engine (System.Text.RegularExpressions) rather than RE2. This is an accepted deviation from upstream (which uses re2j); the vast majority of Copybara patterns behave identically.
• Starlark configuration semantics are preserved by porting the Bazel Starlark interpreter to C# (see src/Starlark).

License

Apache License 2.0 — see LICENSE. Copybara is a trademark of Google LLC; this is an independent port.